Move Configurations to Separate Class in Code-First:

By now, we have configured all the domain classes in OnModelCreating method in the previous sections. When you have a large number of domain classes, then configuring every class in OnModelCreating can become unmanageable. Code-First enables you to move all the configurations related to one domain class to a separate class.

In the below example, we configured Student entity.

public class SchoolDBContext: DbContext

{

    public SchoolDBContext(): base()

    {

    }

    public DbSet<Student> Students { get; set; }

    public DbSet<Standard> Standards { get; set; }

    public DbSet<StudentAddress> StudentAddress { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)

    {

            modelBuilder.Entity<Student>().ToTable("StudentInfo");

            modelBuilder.Entity<Student>().HasKey<int>(s => s.StudentKey);

            modelBuilder.Entity<Student>()

                    .Property(p => p.DateOfBirth)

                    .HasColumnName("DoB")

                    .HasColumnOrder()

                    .HasColumnType("datetime2");

            modelBuilder.Entity<Student>()

                    .Property(p => p.StudentName)

                    .HasMaxLength();

                modelBuilder.Entity<Student>()

                    .Property(p => p.StudentName)

                    .IsConcurrencyToken();

            modelBuilder.Entity<Student>()

                .HasMany<Course>(s => s.Courses)

                .WithMany(c => c.Students)

                .Map(cs =>

                        {

                            cs.MapLeftKey("StudentId");

                            cs.MapRightKey("CourseId");

                            cs.ToTable("StudentCourse");

                        });

    }

}

Now, you can move all the configurations related to Student entity to a separate class which derives from EntityTypeConfiguration<TEntity>. Consider the following StudentEntityConfigurations class.

public class StudentEntityConfiguration: EntityTypeConfiguration<Student>

{

    public StudentEntityConfiguration()

    {

            this.ToTable("StudentInfo");

            this.HasKey<int>(s => s.StudentKey);

            this.Property(p => p.DateOfBirth)

                    .HasColumnName("DoB")

                    .HasColumnOrder()

                    .HasColumnType("datetime2");

            this.Property(p => p.StudentName)

                    .HasMaxLength();

            this.Property(p => p.StudentName)

                    .IsConcurrencyToken();

            this.HasMany<Course>(s => s.Courses)

                .WithMany(c => c.Students)

                .Map(cs =>

                        {

                            cs.MapLeftKey("StudentId");

                            cs.MapRightKey("CourseId");

                            cs.ToTable("StudentCourse");

                        });

    }

}

As you can see above, we have moved all the configuration for the Student entity into constructor of StudentEntityConfiguration, which is derived from EntityTypeConfiguration<Student>. You need to specify entity type in a generic place holder for which you include configurations, Student in this case.

Now, you can inform Fluent API about this class, as shown below.

public class SchoolDBContext: DbContext

{

    public SchoolDBContext(): base()

    {

    }

    public DbSet<Student> Students { get; set; }

    public DbSet<Standard> Standards { get; set; }

    public DbSet<StudentAddress> StudentAddress { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)

    {

            // Moved all Student related configuration to StudentEntityConfiguration class

            modelBuilder.Configurations.Add(new StudentEntityConfiguration());

    }

}

Thus, you can use a separate class to configure a domain class to increase the readability and maintainability.

巴特西

Entity Framework Code-First（16）：Move Configurations

Move Configurations to Separate Class in Code-First:

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